This invention generally relates to the field of ballistics, and it particularly relates to recoilless gun systems such as the xe2x80x9cDavis gunxe2x80x9d system described in U.S. Pat. No. 1,108,714. More specifically, the present invention relates to a contained Davis gun system that enables misfire and hang-fire handling for fire out of battery, that decreases structural dynamic activity of the gun barrel during launch with resulting increases in system accuracy, that possesses an almost infinitely variable chamber volume and a potential for direct fire xe2x80x9czoningxe2x80x9d, with a reduced system weight, and that presents synergistic advantages when combined with a conventional recoil system in a double recoil design.
A xe2x80x9cDavis gunxe2x80x9d system is known where the propellant gas pressure is inertially contained. A projectile is fired toward the front and a compensating mass toward the rear from an equal-caliber barrel open on both ends. The axial forces are transmitted to the gun only by friction of the projectile and/or the compensating mass on the inner wall of the barrel; propellant gas forces in this case do not contribute toward recoil during firing, and the friction forces can be kept lower by several orders of magnitude than the propellant gas forces, while the friction forces of the projectile and of the compensating mass, at least in part, compensate each other. For this reason, the so-called xe2x80x9cDavis gunxe2x80x9d is an essentially recoilless gun.
Conventional gun systems still present some or all of the following concerns and none provided an integral, fully satisfactory solution to such concerns.
Conventional gun systems are awkward to operate in the fire out of battery mode. Fire out of battery is a technique to reduce the magnitude of the forces applied between the gun mount/platform and those parts of the gun that recoil during firing. It is achieved by pre-accelerating the recoiling gun mass forward, prior to firing. Thus, upon firing, the rearward momentum applied to the recoiling gun parts by the containment of the propellant gas pressure is directly offset by that portion imparted to the gun prior to firing. Theoretically, since half of the momentum may be applied prior to firing, the maximum speed of recoil may be cut exactly in half. Since the kinetic energy is related to the square of velocity and is achieved by the recoil forces applied over the available recoil stroke, the recoil forces may be theoretically cut by a factor of four. Conservation of momentum is achieved by increasing the duration of the recoil forces, again by a factor of four.
Two principal engineering challenges hinder the application of fire out of battery to conventional gun systems. First, in the event of a misfire, the forward momentum of the pre-accelerated recoiling gun parts is not reversed by the reaction of the gun to firing the projectile forward. As a consequence, the forward momentum and its associated kinetic energy must be extracted in a controlled fashion to prevent damage resulting from the impact of the gun against the gun mount as it reaches the end of the available recoil travel stroke. This requires a shock isolator termed a misfire snubber. Since fire out of battery is applied principally to attenuate the recoil forces (or reduce the required recoil stroke), the magnitude of the snubber loads are also generally limited. In the event the snubber loads are required not to exceed the same maximum loads as the pre-acceleration loads, it may be seen that kinetic energy imparted to the gun over the intended recoil stroke prior to firing will require exactly the same stroke length to safely decelerate the gun to a standstill in the event of a misfire. Thus half of the total available recoil stroke would have to be dedicated to misfire snubbing. Since the same kinetic energy is required to pre-accelerate to half of the forward momentum regardless of how misfire is addressed, it may be seen that under the assumptions made, the maximum recoil forces must be doubled relative to those of the theoretical minimum. Thus, relative to the standard fire in battery mode, the fire out of battery mode that incorporates such a misfire snubber may only cut recoil loads by a factor of two.
The second principal challenge that hinders the application of fire out of battery to conventional gun systems is hang fire. Hang fire is the delayed ignition of a round of ammunition and is relatively rare. The extreme situation of hang fire for a fire out of battery gun system would be the delay of shot start ignition until after the misfire snubber had brought the forward momentum of the gun system to rest; thus, in this context, a misfire is a necessary prerequisite to a hang fire, but only a few misfires become hang fires. When such a hang fire occurs, no forward momentum remains to offset the rearward momentum imparted to the gun system by its reaction to firing. Therefore, the recoiling gun mass may recoil with double the speed of the ideal fire out of battery design, and thus four times the kinetic energy. This dramatic increase in kinetic energy must be extracted using the integral of recoil force over recoil stroke. It is obvious that design of a conventional gun system to withstand hang fire is the exact same problem as the conventional fire in battery mode of operation, thus negating much of the impetuous for incorporating a fire out of battery design in the first place.
xe2x80x9cGun whip,xe2x80x9d that is the motion of a gun barrel during in bore gun dynamics, can become excessive when the gun barrel itself recoils. This recoil acceleration of a traditional barrel is a significant contributor to the gun barrel dynamic flexure that results in increased round dispersion. In addition, the ability to increase the structural stability of conventional gun systems using external xe2x80x9ctruss likexe2x80x9d structures to increase the flexural rigidity of the launch tube is hindered by concerns about the effects of recoil upon such structures. Furthermore, in the absence of such external structures high emphasis is placed upon the flexural rigidity of the gun barrel itself, therefore, the application of non-homogeneous manufacturing techniques, such as composite or wire wrapped guns are impeded.
The required flexural rigidity of Conventional gun systems impairs xe2x80x9cfine tunexe2x80x9d stabilization capability for enabling the gun muzzle to bend to the target. In the absence of recoil acceleration, most of the remaining gun dynamic loads associated with launch including centripetal acceleration of the projectile and gases increase as a function of the non-ideal curvature of the centerline of the gun barrel and the projectile velocity which is quite low near the breechblock end.
Conventional gun systems employ the integrity of steel to contain the rearward reaction force of the gun launch created by the internal pressures applied over the exposed breechblock area using stress developed as the breechblock material undergoes strain. They require a breech ring, breechblock, and threads applied to the rear of the gun barrel to contain the rearward force of the high pressure propellant gases, thus increasing the ultimate weight of the gun system.
Numerous attempts were proposed to address the foregoing concerns. One such attempt that aims at reducing the recoil forces associated with the reaction of a recoiling gun to firing is to increase the recoil stroke. Compared with the theoretical limit of implementation of the current invention, increasing the recoil stroke of any gun system by a factor of four may reduce the recoil force by a factor of four. Long recoil strokes are undesirable for a number of reasons for most applications. First, the longer the recoil stroke the more substantial and complicated the gun mount becomes. For turreted gun systems, the need to be able to point the gun at different elevations and azimuthal orientations results in a spherical sweep volume that increases with the cube of the distance between the furthest extent of recoil and the trunnion bearings. This sweep volume is very wasteful and requires substantial armor to protect.
Some gun systems apply muzzle brakes to reduce the forward momentum imparted to the propellant gases. These function by redirecting the gas flow velocity vector so the forward component is reduced, or even reversed if the muzzle brake bends the gas flow by more than 90 degrees. One of the preferred embodiments of the current invention is fully compatible with muzzle brakes.
A recoilless gun, such as the M40AD 106 mm recoilless rifle, is a gun system that achieves a momentum balance by ejecting high velocity propellant gases in a direction opposite to the projectile launch. In analogy, the xe2x80x9cDavis gunxe2x80x9d launches momentum carrying inertia (manifest as a projectile composed of lead shot) rearward without recapturing the inertia for later use.
However, these attempts were not completely successful in addressing and resolving all the foregoing design concerns. For a Davis gun that shoots a dummy projectile rearward in addition to the ordnance projectile that is fired forward, all the energy applied to the rearward projectile is wasted in the sense that it is not applied to defeat a target. The higher this mass, the less energy is required to balance the momentum. However, the higher this mass, the greater the logistical burden to supply the ammunition to the field. A Davis gun barrel must contain the pressure of the propellant gases. Since the dummy mass slides rearward, additional requirements (i.e., weight) will be required to contain these gases over the rearward stroke.
A recoilless gun expends significant propellant energy sending the high velocity and lightweight propellant gases rearward. In addition, a recoilless rifle also needs to vent these gases rearward, and must overhang the end of the fighting vehicle to which it is mounted. This is a burden for reloading the guns. The nozzle design requirements and high energy gases limit the operating pressure of recoilless guns.
It is an object of the present invention to address and satisfactorily resolve the above concerns, and to provide a gun system that enables misfire and hang-fire handling for fire out of battery, that decreases structural dynamic activity of the gun barrel during launch with resulting increases in system accuracy with a reduced system weight, and that presents synergistic advantages when combined with a conventional recoil system that may incorporates a muzzle brake in a double recoil design.
The present invention enables the use of the intended launch stroke to provide a sufficiently long misfire snubber that would subsequently allow sufficient snubber stroke to contain a hang fire without excessive recoil force. In other terms, in the event that a round of ammunition misfires, the round and the inertial breechblock are free to travel down the prismatic bore of the gun as they are decelerated. The deceleration trajectory may be designed such that the combined stroke available between the intended recoil stroke and that traversed by the misfire snubber is sufficient to extract the kinetic energy imparted to the inertial breechblock upon a hang fire with out exceeding the design recoil force limits. In the event of such a hang fire, the interior ballistics travel of the projectile would be cut short from the intended bore travel by the snubber stroke.
The present invention further enables the forward ejection of any round that is no longer deemed a viable round for any reason. For example, the breechblock need not be opened following a misfire. The round may merely be ejected out of the muzzle. Similarly, the gun barrel may be used as the reload port to upload rounds from an external resupply source.
The foregoing and additional features of the present invention are realized by a gun system that includes a non-recoiling barrel and a recoil system secured to the barrel or the firing platform. The recoil system includes a brake and a spring secured to a mount fixture. The gun system further includes an inertial breechblock housed within the barrel, and capable of translating within the barrel. The breechblock enables the loading of the propellant and the projectile within the barrel, and further enables pressure to be contained within the barrel during firing. The recoil system applies a load to the inertial breechblock, which is a function of the breechblock position and its velocity within the barrel. A part of the kinetic energy imparted to the breechblock by the gun system reaction to firing is stored as potential energy within the spring, and any remaining kinetic energy is dissipated by the brake as heat.
Prior to firing, the barrel and the recoil system are coupled to the firing platform. When the propellant is ignited, propellant gases generated by the propellant propel the projectile forward along the gun barrel while propelling the inertial breechblock rearward with compensating momentum. At shot exit, when the projectile exits the barrel, the breechblock begins to engage the recoil system. The rearward free recoil deflection of the breechblock that occurs prior to shot exit and engagement of the inertial breechblock with the recoil system may be computed by dividing the sum of deflection and mass products for the projectile and propellant gases by the mass of the breechblock. After the shot exit the breechblock is decelerated by the recoil system.
According to another embodiment, the gun barrel and the recoil system are coupled to the firing platform, and the projectile and the breechblock are pre-accelerated forward by the recoil system prior to the ignition of the propellant.
Upon firing the projectile, the reaction of the breechblock is manifest as a rearward velocity and subsequent kinetic energy. The goal of the recoil system is to design it such that the kinetic energy of the reversed breechblock is equal to the kinetic energy that the recoil system imparts to the breechblock and to the projectile prior to firing. The propellant is ignited upon reaching a predetermined firing location and velocity selected to minimize a load required by the recoil system load over a recoil stroke for both a pre acceleration stroke and a deceleration stroke. Just prior to, and after shot start, the breechblock continues to slide forward some distance until its momentum is reversed by the force of the propellant gases. Shortly after shot exit, during the containment of the recoiling breechblock, the kinetic energy of the breechblock following the shot exit is converted into potential energy of the recoil system spring.
According to still another embodiment, the gun barrel begins to move rearward as soon as the breechblock is released and pre-accelerated forward, and the recoil system includes primary and secondary recoil systems. Prior to firing, a load between the barrel and the breechblock is decoupled from a platform by the secondary recoil system. The secondary recoil system is attached to the platform, and may include a muzzle brake that redirects the flow velocity of a portion of the propellant gases rearward after shot exit, which would result in a large forward load applied to the barrel at the muzzle brake.
The gun systems of the present invention offer several advantages, some of which are listed below.
1. Fire out of battery, also known as xe2x80x9csoft recoilxe2x80x9d, is facilitated by three properties:
1.A. In the event of a misfire, the entire travel length of the gun barrel is available for deceleration of the forward momentum of the combined inertial breechblock and round. Misfire handling is a principle disadvantage of fire out of battery and is solved using a contained Davis gun system of the present invention. In a Davis gun system, the rearward projectile is expelled from the gun system. According to the present, the rearward projectile is not expelled, but is rather captured or contained by the recoil system, wherefore, the designation xe2x80x9ccontained Davis gun systemxe2x80x9d.
1.B. In the event that a round has misfired, or is no longer deemed a viable round for any reason, it may be ejected out of the muzzle of the barrel (e.g. pneumatic ejection). The present contained Davis gun systems eliminate the chamber geometry that prevents the forward ejection of xe2x80x9cbadxe2x80x9d rounds.
1.C. In the event that a round experiences hang-fire, the momentum may be extracted by the recoil system over the combined stroke of the misfire snubber and intended recoil stroke, thus keeping forces low. The misfire snubber stroke is sufficiently long to enable tolerable recoil forces to be applied.
2. xe2x80x9cGun Whipxe2x80x9d, that is the motion of a gun barrel during in bore cannon dynamics is greatly reduced as the cannon barrel itself no longer recoils. This recoil acceleration of a traditional barrel is a significant contributor to the gun barrel dynamic flexure that results in increased round dispersion. This is particularly true of gun barrels that are pre-accelerated forward to effect fire out of battery and are thus vibrationally disturbed by these forces prior to firing.
Gun whip may also be reduced by the ability to structurally stabilize the cannon using external xe2x80x9ctruss likexe2x80x9d structures to increase the flexural rigidity of the launch tube without concerns about the effects of recoil acceleration upon such structures.
With the decreased emphasis placed upon the flexural rigidity of the cannon barrel itself, non-homogeneous manufacturing techniques, such as composite or wire wrapped guns may become more viable. Similarly, with the decoupling of the cannon barrel mass from the recoiling gun system mass, lightweight cannon manufacturing materials may become more viable.
3. Smart structure technology, using sensors, actuators, and control mechanisms, is also facilitated by the removal of the gun barrel from the shock and vibration environment of recoil. This enables simplified application of sensors and actuators to the structure. Smart structure technology is also facilitated by the decreased flexural rigidity of gun barrels making active bending of the barrels easier for the actuators.
4. Gun barrels manufactured of non-homogenious materials, such as the wire wraped gun, that are facilitated by the present invention are easier to bend into desired shapes, thus increasing the controllability of the gun systems enabled by the present invention. A xe2x80x9cline tunexe2x80x9d stabilization could be applied to the muzzle end of the gun barrel, literally bending the gun muzzle to the target. An important consideration of such a stabilization technique for a conventional gun system would be the xe2x80x9cgun whipxe2x80x9d described herein.
In the absence of recoil acceleration, most of the remaining gun dynamic loads associate with launch including centripetal acceleration of the projectile and gases increase as a function of the non-ideal curvature of the centerline of the gun barrel and the projectile velocity. Therefore, intentional flexure induced near to the breechblock of the gun barrel where the round velocity is slow, will not result in large dynamic loads and subsequently launcher flexure and dispersion.
5. The ultimate weight of a gun system may be reduced. The present invention uses inertial containment of the propellant gas pressure. Conventional gun systems use the integrity of steel to contain the pressure using stress developed as the material undergoes strain. Inertial containment obviates the need for a breech ring, conventional breechblock, and threads applied to the rear of the gun barrel.
It is very possible that the inertia used to contain the propellant gas pressure could serve a dual use. For example, the inertial breechblock could be directly coupled to the rear armor plate of an oscillating turret. Thus, the mass of the armor would directly reduce the recoil energy without requiring additional system burden.
With reduced emphasis placed upon flexural rigidity, the application of lightweight composite materials to reduce launcher mass is facilitated.
By enabling fire out of battery, less emphasis will be placed upon maintaining a large recoiling inertia of the gun system. By conservation of momentum a large recoiling mass reduces the kinetic energy imparted to the gun system. The relationship is inversely proportional; e.g., if the recoiling mass were doubled, the energy is cut by a factor of two. Using simple physical models, an idealized fire out of battery gun system may reduce the kinetic energy by a factor of four with respect to its fire in battery counterpart. Thus, far less system mass is required to maintain kinetic energy levels of the recoiling gun system at manageable levels.
7. The contained gun systems of the present invention may be combined with a conventional recoil by employing a double recoil system. Using this approach, the benefits of fire out of battery may be realized using the present inventive technology, while the recoil energy imparted to the gun system by conservation of momentum may be reduced by leveraging the inertia of the entire barrel.
A double recoil system would also enable muzzle brakes to be applied to the cannon barrel while isolating the resulting shock load from the weapon platform using a secondary (gun barrel) recoil system.